Primary cells having charge transfer complexes such as iodine-containing material are known. For example, cells utilizing iodine-containing charge transfer complexes as cathodes and anodes of selected divalent metals have been disclosed by Gutman et al, J. Electrochem. Soc. 114, 323 (1967). Also, high energy density batteries utilizing a lithium anode and cathode of organic materials such as polycyclic aromatic compounds, organic polymers, heterocyclic nitrogen containing compounds and the like and iodine have been disclosed, U.S. Pat. No. 3,660,163.
Improved cathode compositions comprising a mixture of iodine and poly-2-vinypyridine . nI.sub.2 or poly-2-vinyquinoline . nI.sub.2, where n =2-15, have been taught. See U.S. Pat. No. 3,674,562, incorporated herein by reference. Cathode material of the latter type is typically a pliable, plastic-like solid. In other applications the cathode material is viscous substance that has a proclivity to flow.
Since the lithium halide batteries are typically used with implantable prosthetics such as cardiac pacemakers, it is necessary that they be physically small, and highly reliable. Various lithium battery enclosures have been proposed to contain the iodine cathode material from flowing and forming a short circuit between the anode and cathode. For example, U.S. Pat. No. 3,723,183 a lithium battery enclosure is disclosed in which a lithium anode is formed as the inner surface of a steel battery container. The iodine-containing cathode material is then pressed into the lithium layer. A shoulder is thereafter formed on the lithium layer and precision fit with a cap to contain the cathode. The cap includes an aperture through which an insulated lead provides electrical contact with the cathode. A material such as epoxy is formed over the cap to hermetically seal the battery.
Enclosures such as the one described in U.S. Pat. No. 3,723,183 have a number of commercial disadvantages. For example, the voided space provided between the cathode material and cap physically enlarges the size of the battery as well as permits oxidation of the lithium material, even with dry air. Further, it is difficult in practice to maintain the cap receiving shoulder sufficiently clean to obtain a diffusion bond or weld when the cap is pressed thereon. Thus, there is no way to check whether the battery will leak until it has been completely assembled with the hermetic seal. A further disadvantage is that the outer case is necessarily the negative terminal of the cell since it is common with the lithium.
One commercially satisfactory method of assembling lithium-iodide cells utilizes an internal plastic encapsulating member to contain the active cell components. In these batteries, a lithium anode surrounded by the cathode material is encased in a plastic case which is fitted within a metal outer case. The plastic encasements, however, have two substantial disadvantages: (1) the plastic encasing material occupies space which could be preferentially used for the active cell material, and (2) the adhesive used to cement the plastic material closed is subject to attack by the active species from the electrolyte or cathode causing physical deterioration and/or a decrease in resistivity.
Accordingly, it is an object of the present invention to provide a lithium anode cell that minimizes the quantity of plastic to afford either a size reduction in the completed assembly or utilize more active components. It is a further object of the invention to provide a cell that has no air or void spaces, shows increased contact area between anode and electrolyte, and can be tested for leakage prior to complete assembly. Further, it is an object of the invention to provide a cell having increased voltage under load, decreased internal impedance, and a larger electrical capacity compared to plastic encased lithium anode cells of the same size.